Azure Container App mounted volume - permission denied

Question

My c# .net core 5 application running in azure container environment as azure container app with azure file mounted as a persistent volume suddenly started to throw UnauthorizedAccessException (see below).

It was all working fine until recently. The azure file is setup in read/write access mode and mounts to the container without any issue. The application reads from the volume but when it tries to write only the file is created and then the exception is thrown.

System.UnauthorizedAccessException: Access to the path '/app/Card/IMPORTINTERNATIONAL/EXP_3_20231129_1.XML' is denied.
 ---> System.IO.IOException: Permission denied
   --- End of inner exception stack trace ---
   at System.IO.FileStream.WriteNative(ReadOnlySpan`1 source)
   at System.IO.FileStream.FlushWriteBuffer()
   at System.IO.FileStream.Dispose(Boolean disposing)
   at System.IO.Stream.Close()
   at System.IO.StreamWriter.CloseStreamFromDispose(Boolean disposing)
   at System.IO.StreamWriter.Dispose(Boolean disposing)
   at System.IO.TextWriter.Dispose()
   at PCES.CardService.Web.Controllers.QPCController.<>c__DisplayClass25_0.

Answer 1

The issue has been resolved by changing the file create/update with the following code:

new FileStream(filename, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None)

The problem was probably coming from the CIFS mount implementation.